Turkish Prime Minister Recep Tayyip Erdogan's ally-turned-rival Fethullah Gulen is suing him in the wake of a deeply damaging corruption scandal, a newspaper close to Gulen's movement reported today.

Gulen, an Islamic preacher living in self-imposed exile in the United States, is claiming 100,000 lira (32,700 euros, $44,200) in damages from Erdogan for allegedly denigrating and insulting remarks, the Zaman daily said.

Erdogan, 59, Turkey's strongman premier since 2003, has blamed a "parallel" state of Gulen's associates within the judiciary and police for a major graft probe that opened in December implicating members of Erdogan's inner circle and their families.

Erdogan has sacked or reassigned hundreds of police and prosecutors, portraying the allegations of shady dealings as part of a plot to weaken his government ahead of local elections on March 30 and a presidential poll in August.

The purges, coupled with a heavy-handed police crackdown on protests last June, moves to exert more control on the judiciary and mooted Internet legislation have raised deep concern at home and abroad about mainly Muslim Turkey.

Gulen's Hizmet movement does indeed wield considerable influence in the judiciary and police but he has denied being behind the corruption probe.

His organisation issued a statement last month saying the government "seems to be poisoned with power".

The Journalists and Writers Foundation, a group linked to Gulen, listed today a string of recent "deeply worrying developments" that risk making Turkey "lose its character as a state governed by the rule of law".

It said these included limits on the freedom of expression, unlawful wiretaps, "purging" civil servants, pressure on the media, the use of "hate-centred language", accusations of "treason" and efforts to place the judiciary under government control.